Interference is probably the single biggest threat to the continuance of
the hobby for those with an urban or suburban location particularly in
the HF spectrum.
In 2006 we had a fairly major house extension, which meant I had to go
QRT for about a year. When I started to get QRV again I discovered I had
lots of EMC issues, mostly interference to me. The majority of it was
due to domestic electrical items that had appeared in our house, either
associated with the extension or due to the rise in popularity of the
switch-mode power supply in the intervening period.
The following pages are further adventures in EMC from the new QTH
in Lawshall, Suffolk.
One of the best articles I've seen on explaining the sources of RFI and
how to deal effectively with them is at
http://audiosystemsgroup.com/RFI-Ham.pdf.
You might also find
GM3SEK's
pages helpful.